11 Preflop GTO: Opening, 3-Bet/4-Bet & Defense Ranges

Preflop is the most-played street in poker. You make a preflop decision on every single hand you are dealt, and the range you enter the pot with constrains everything that happens afterward. Get your preflop ranges roughly right and your postflop game has a fighting chance; get them badly wrong and no amount of clever river play will rescue you. This chapter builds a game-theory-optimal (GTO) baseline for 100bb cash games — the equilibrium ranges that are difficult to exploit — and explains the logic well enough that you can reconstruct a chart from principles when you have forgotten the exact cells.

A word on what “GTO preflop” means in practice. The ranges in this chapter are close approximations of what modern solvers (PioSOLVER, GTO Wizard, Simple Postflop, and similar tools) output for heads-up-display-free, 100bb, standard-rake equilibrium play. They are not gospel — solver outputs shift with rake, antes, stack depth, and bet sizing assumptions, and real opponents are rarely at equilibrium. Treat these as your default, the ranges you fall back to when you have no read, and the reference point you deviate from when you do.

11.1 Position Is the Master Variable

Every preflop range is a function of one dominant input: how many players act after you. The later your position, the more hands you can profitably play, because fewer opponents remain to wake up with a big hand and because you will more often have position postflop.

We use standard 6-max position names: UTG (under the gun, first to act), HJ (hijack), CO (cutoff), BTN (button), SB (small blind), BB (big blind). Full-ring (9-handed) adds earlier seats, conventionally UTG, UTG+1, UTG+2 (sometimes called the “early” block) ahead of the HJ/LJ.

Key idea

There is no single “good starting hand” list. A hand’s playability is entirely contextual. 7 6 is a clear open on the BTN and a clear fold UTG at a full table. K J is a premium UTG hand but a marginal flat against a 3-bet. Stop memorizing hands and start memorizing positional ranges.

11.2 Raise-First-In (RFI) Ranges

When the pot is unopened and it is your turn, you either fold or raise. Limping (just calling the big blind) is essentially never part of an equilibrium RFI strategy outside of specific SB constructions — limping caps your range and invites the BB to attack. Raise or fold.

Open sizing

6-max, 100bb online: Typical opens are 2.0–2.5bb from all positions, with many solver solutions favoring a flat 2.5bb or even a position-dependent ramp (smaller late, larger early). A common simplification: open 2.5bb from every seat.
Live cash: Because live tables call more and play more passively, 3bb to 4bb (or “pot”) opens are standard and correct — you want a larger bet to charge the loose callers and to build a pot you have an equity edge in.
From the SB: open larger, often 3bb, because you will be out of position the whole hand and want to discourage the BB’s wide, cheap defense.

The smaller the open, the wider you can profitably open (you risk less to win the blinds), but the more the blinds can defend. These two forces roughly cancel, which is why 2.0–2.5bb opens with appropriately wide ranges form a stable equilibrium online.

RFI by position (6-max, ~100bb)

The table below gives approximate opening frequencies and the character of each range. Frequencies are expressed as a percentage of all 1,326 starting combinations.

Position	RFI % (approx.)	Character of the range
UTG	~15–18%	Tight, value-dense: big pairs, big broadways, strong suited aces
HJ	~19–22%	Adds more suited connectors and mid pairs
CO	~26–30%	Wide; most suited hands, all pairs, many offsuit broadways
BTN	~42–48%	Very wide; any pair, most suited, many offsuit gappers
SB	~36–44%	Wide but raise-or-fold; a “complete/limp” range exists vs. some configs

UTG (~15%) is the anchor everyone should know cold:

All pairs 22+ (small pairs are a slight open, partly for set-mining and balance)
A T s+ (suited aces ATs and better), plus A5s–A2s as occasional balancing bluffs
A J o+ (offsuit aces AJo and better)
K T s+, Q T s+, J T s, and the broadway offsuit hands K Q o (sometimes K J o)
Suited connectors roughly T9s–98s as the bottom of the suited bluffs

BTN (~45%) is the widest non-blind range. From the button you open essentially:

Every pocket pair
Every suited ace, every suited king down to about K 5 s, most suited queens and jacks
All suited connectors and one-gappers down to about 54s
A wide swath of offsuit broadways and offsuit aces (A 2 o+ in many solutions), K 9 o+, Q 9 o+, J 9 o, T 9 o

Common mistake

Opening too wide from early position is the single most common preflop leak in low-stakes games. A 25%+ UTG range looks aggressive and “modern,” but you will be out of position with too many dominated hands. When in doubt UTG, fold the offsuit junk and the weak suited gappers. Tight-and-aggressive from up front, loose-and-aggressive from the button.

Full-ring differences

Full-ring (9-max) is tighter in every early seat because there are simply more players left to act. A 9-max UTG range is closer to 10–13% — basically the 6-max UTG range minus the speculative suited connectors and weakest suited aces. By the time the action folds to the CO and BTN, the ranges converge with 6-max because the number of players behind is the same. The practical rule: in full ring, add roughly one extra fold-tier to each of the first three seats, then play 6-max ranges from HJ onward.

11.3 3-Betting: Linear vs. Polarized

When someone opens and you want to re-raise, your 3-bet range takes one of two shapes:

Linear (merged): all of your strongest hands — you 3-bet the top of your range and flat or fold the rest. Used when the caller behind you is weak/passive, when you are against a very wide opener you dominate, and often from the blinds where you have no position to protect.
Polarized: your strongest value hands plus a selection of weak-but-playable bluffs (often suited wheel aces and suited connectors/gappers), while hands of middling strength are flatted instead. Used in position against a reasonable opener, where flatting your medium hands realizes equity better than bloating the pot with them.

Why polarize in position?

Imagine the CO opens and you are on the BTN with K Q o. This hand is too strong to fold but plays beautifully as a flat: you keep dominated hands like K J o and Q J o in the opener’s continuing range and you realize equity with position. If instead you held A 5 s — a hand with a nut blocker, decent equity when called, but poor flatting value — it makes a far better 3-bet bluff. So your BTN 3-bet range becomes polarized: A A–Q Q, A K, A Q s for value at the top; A 5 s–A 4 s, K 5 s, suited gappers as bluffs at the bottom; and the K Q o / J J / A Q o “middle” goes into the flatting range.

Why linearize from the blinds?

From the SB facing a BTN open, you have no position and flatting is dangerous (you will be out of position with a capped range, and the BB can squeeze). So the SB’s main weapon is a linear/merged 3-bet: 3-bet a dense block of your best hands — pairs 55+, A T s+, K Q s, A J o+, K Q o type hands — and fold most of the rest, mixing in some suited bluffs for balance. Solvers do flat some hands from the SB, but the strategy leans far more toward 3-bet-or-fold than the in-position equivalent.

3-bet sizing

In position (e.g., BTN vs CO): smaller, around 3x the open (open 2.5bb → 3-bet ~7.5–8bb). Position lets you use a smaller raise.
Out of position (e.g., BB vs BTN, SB vs CO): larger, around 4x the open (open 2.5bb → 3-bet ~10–11bb), because you need to deny the opener cheap, in-position equity realization.
Live: scale up to account for larger opens and stickier opponents; against a 4bb open, a 3-bet to ~12bb in position / ~14bb out of position is reasonable.

Key idea

3-bet bluffs are not random trash — they are chosen for two properties: (1) card-removal/blockers (A 5 s blocks A A, A K, and A Q, reducing the chance the opener has a 4-bettable hand) and (2) playability when called (suited wheel aces and suited connectors flop straights, flushes, and pairs+draws). A 7 2 o has neither property and is never a 3-bet bluff. A 5 s has both.

11.4 4-Betting, 5-Betting & Jamming

When your 3-bet gets 4-bet, or you face a 4-bet after opening, stacks start to commit and ranges get very narrow and value-heavy.

4-bet structure

At 100bb, a 4-bet is itself polarized: a block of value hands that want the money in (roughly Q Q+, A K, sometimes J J / A Q s depending on positions) plus a few bluff 4-bets chosen — again — for blockers. The canonical 4-bet bluff is A 5 s (or A 4 s, A 5 o), because the ace blocks A A and A K, the two hands most likely to continue against your 4-bet. Sizing for a 4-bet at 100bb is typically to about 2.2–2.5x the 3-bet out of position and a bit smaller in position — large enough to set up a stack-off but not so large you have no fold equity.

The commitment math

Once a 4-bet goes in, the pot is large relative to the remaining stacks. A hand like A K or K K facing a 4-bet usually wants to either 5-bet jam or call-committed; A A and K K and occasionally Q Q are happy to get 100bb in preflop. The 5-bet at 100bb is almost always all-in (a jam) — there is rarely room for a non-all-in 5-bet — and the 5-bet/jam range is extremely tight: predominantly A A, K K, A K, with Q Q and the A5s-type bluffs mixed in at low frequency to stay balanced.

Common mistake

Stacking off light against a 4-bet/5-bet war. At equilibrium, the player who 4-bets and especially the player who 5-bet-jams is showing a range so strong that calling off with J J, A Q, or even T T is often a losing play against tight opponents. Against unknown but solid regulars, treat a 4-bet as roughly “Q Q+/A K with a few bluffs” and a 5-bet jam as “K K+/A K, maybe A A only.” Fold your bluff-catchers unless you have a specific read that they are over-bluffing.

11.5 Flatting (Cold-Calling) Ranges

Flatting an open — calling rather than 3-betting — is mostly an in-position tool. The strongest flatting spot in poker is the BTN versus a CO or HJ open: you have position, the pot stays small, and you keep the opener’s dominated hands in. A representative BTN flatting range versus a CO open includes:

Mid pairs that don’t want to 3-bet-for-value or get 4-bet off their equity: roughly 2 2–T T (with J J/Q Q sometimes flatting, sometimes 3-betting as a mix)
Suited broadways that dominate-and-are-dominated: A J s, A T s, K J s, K T s, Q J s, J T s
K Q o, A Q o, A J o type hands that prefer to keep the pot small
Suited connectors T 9 s–6 5 s for their postflop playability

Cold-calling out of position (in the blinds or sandwiched between players) is dangerous and largely avoided in solver play, with one giant exception covered next: BB defense. When you do flat out of position, your range gets run over because you are capped (you’d have 3-bet your best hands) and you have to act first on every street.

Common mistake

“Cold-calling in the small blind.” Flatting an open from the SB invites the BB to come along for a cheap price (or squeeze you), and leaves you out of position against two opponents with a capped range. Against most opens, the SB should be 3-bet-or-fold. Only construct a SB flatting range against very wide late-position opens, and even then keep it small and connected.

11.7 The Squeeze

A squeeze is a 3-bet made after an open and one or more callers. It is one of the most profitable and under-used preflop plays, and it has special mechanics:

You get extra dead money. The caller(s) have put chips in without the range strength to continue against a big raise. That dead money improves your immediate price on a bluff.
You apply pressure to the “sandwiched” caller, who is now facing a 3-bet with a capped flatting range (they didn’t 3-bet, so they don’t have the nuts) and players still to act behind.
Size up. Because there are more players and more dead money, squeeze larger than a heads-up 3-bet — a common rule is the base 3-bet size plus about one extra opener-raise per caller. Open 2.5bb, one caller → squeeze to roughly 12–14bb rather than the 10bb you’d use heads-up.

Squeeze ranges are polarized: strong value (Q Q+, A K, A Q s) that wants to play a big pot against the capped callers, plus blocker-heavy bluffs (A 5 s, K Q s, suited wheel aces). Avoid squeezing the medium hands — they’d rather overcall and see a flop multiway.

Drill

Deal yourself 20 hands and, before looking at any chart, classify each one in a fixed spot — say “CO has open-folded to me on the BTN.” For each hand say out loud: open, or fold? Then check against the BTN RFI range above. Repeat for “UTG to act” and “BB facing a 2.5bb BTN open.” Do this until your snap judgment matches the chart 18 out of 20 times. Speed and accuracy on these defaults free your mind for the reads that actually win money.

11.8 A Fully Worked Example

Setup: 6-max, 100bb effective, online, standard rake. Folds to the CO, who opens to 2.5bb. The BTN (a solid, aggressive regular) calls. You are in the BB with A 5 s. The SB folds. Action is on you.

Step 1 — Identify the spot. This is a squeeze spot: an open plus one cold-caller, and you are in the BB closing the action. There is dead money in the SB’s fold and in the BTN’s flat.

Step 2 — Classify the hand. A 5 s is a premier squeeze bluff. The ace blocks A A and A K (the hands most likely to 4-bet or call strongly), the 5 gives wheel and straight potential, and the suit gives flush potential. It is a poor pure flat (dominated-ace problems, out of position, multiway) but an excellent polarized bluff.

Step 3 — Choose the action and size. Squeeze. Because there are three other live ranges and dead money, size up: base out-of-position 3-bet of ~11bb plus roughly one opener-size for the caller → squeeze to about 13bb.

Step 4 — Reason through the responses.

The CO opened a ~27% range from the cutoff. Against a large BB squeeze, most of that range (the suited gappers, the offsuit broadways, the small pairs) has to fold. The CO continues with roughly Q Q+, A K, A Q s, and a few bluff 4-bets / strong flats. You hold a card-removal advantage: your ace makes their A A and A K less likely.
The BTN flatted, which caps their range — they almost certainly don’t have A A/K K (those would usually 3-bet themselves). Facing your squeeze plus a still-live opener, the BTN’s flat-behind range is fragile and folds often.
When everyone folds, you scoop the dead money immediately — the primary way this hand profits.
When you do get called or 4-bet, A 5 s still flops reasonably and your ace-blocker means the 4-bets you face are weighted toward the genuine nut hands (fold) rather than bluffs.

Step 5 — The takeaway. You are not squeezing A 5 s because it’s a strong hand — it isn’t. You’re squeezing because the structure (dead money + a capped caller + your blockers) makes a polarized re-raise more profitable than folding or flatting. Swap your cards for K Q o and the better play is usually to fold or, against a wide CO, to flat in position — but you are out of position here, so K Q o’s flatting value drops and folding is fine. Swap them for Q Q and you squeeze for value at the same size. Same spot, three different hand classes, three different reasons.

11.9 Putting It Together: A Reference Hierarchy

When you sit down at 100bb, carry this mental scaffolding:

Unopened pot: raise or fold per your positional RFI. Tight UTG, exploding wide by the BTN. Never limp.
One raise in front, you’re in position: polarized 3-bet (value + blocker bluffs) or flat your medium hands or fold the rest.
One raise in front, you’re out of position (blinds): lean toward linear/merged 3-bet-or-fold; the BB additionally defends very wide by calling because of the price.
Raise + caller(s): consider the polarized squeeze, sized up for the dead money.
Facing a 4-bet: narrow to value (Q Q+, A K) plus a sprinkle of A5s-type bluffs; everything in between folds.
Facing a 5-bet jam at 100bb: continue only with the very top — roughly K K+/A K — unless you have a concrete read that they are jamming light.

These are your defaults — the equilibrium you return to when the table gives you nothing to exploit. The next chapters take these baselines and bend them: when a player opens too wide, you 3-bet wider and call down lighter; when a player only 4-bets the nuts, you fold every bluff-catcher and re-bluff relentlessly. But you cannot deviate intelligently from a baseline you don’t own. Drill these ranges until they’re automatic, and the thinking part of your brain is freed for the part of poker that actually beats other humans: reading them.

11.1 Position Is the Master Variable

11.2 Raise-First-In (RFI) Ranges

Open sizing

RFI by position (6-max, ~100bb)

Full-ring differences

11.3 3-Betting: Linear vs. Polarized

Why polarize in position?

Why linearize from the blinds?

3-bet sizing

11.4 4-Betting, 5-Betting & Jamming

4-bet structure

The commitment math

11.5 Flatting (Cold-Calling) Ranges

11.6 Big-Blind Defense Is Wide

11.7 The Squeeze

11.8 A Fully Worked Example

11.9 Putting It Together: A Reference Hierarchy